The present invention relates to apparatus for stabilizing the rocker arm assembly of stud mounted rocker arm designs in internal combustion engines operating at high RPM, i.e., from 5000 rpm to 7000 rpm and above. The invention is applicable to both lifter type and overhead cam type engines that employ stud mounted rocker arms.
Stud mounted rocker arm assemblies have been adapted for many high performance, high rpm engines, particularly those used in racing. Without stabilization, stud mounted rocker arm are often subject to premature fatigue failure. Even when failure does not result, adverse harmonic vibrations spoil engine performance. Races have been lost to this problem since these parts cannot be replaced within the time constraints of the racing situation. Furthermore, even where stud girdles have been used they have not functioned well at very high rpms resulting in rough engine performance or difficult adjustment.
Heretofore, girdle bars and plates have been clamped sidewise to several of the studs at once in order to distribute vibration and to tie the rocker arm structure together. Such girdle bar mechanisms are shown in U.S. Pat. No. 3,870,024 to Ridgeway, issued Mar. 22, 1975 and U.S. Pat. No. 3,430,612 to Anseth issued Mar. 4, 1969.
Both of these reference patents propose a mechanical arrangement in which a clamp is formed by squeezing a pair of girdle bars partially encircling the studs with a small gap between the girdle bars with a set of screws operating intension. This causes the included girdle pairs to clamp the studs laterally, i.e., normal to the axis of the stud. In the so-called Chevy V-8 heads, the studs are aligned parallel and in the same plane which makes for relatively simple machining of the recesses for such prior girdles. However, in the Ford V-8 head the valves are canted and splayed so that there is no common alignment. Economic machining of a girdle for such an arrangement has not been possible not only due to the required resetting and rejigging of the machine tools, but also because the installation becomes too critical.
The designs of U.S. Pat. Nos. 3,430,612 and 3,870,024 references rely on screws in tension for the clamping forces. As known, tensioned screws have considerable yield and the result is not fully effective as the operating forces increase. In most cases, moreover, the removal of the girdle, which must be done several times before each race, requires several very inconvenient and time-consuming steps; requires the use of both of the mechanic's hands, one to back the other end of the screw while the first is removed. While one handed arrangements appear to be shown in U.S. Pat. No. 3,430,612 they are impractical for other reasons. There is, therefore, a need for a new and improved girdle assembly which will overcome the above limitations and disadvantages.
In general, it is an object of the present invention to provide an improved valve stud girdle which is self-aligning to the studs over a suitable range of positions; uses clamping forces developed without screws tension in the plane of the girdle (lateral to the studs), and which can readily be removed and replaced after being installed.
A further object of the invention is to provide a valve stud girdle of the above character which can be set up, removed and reinstalled in a one-handed operation with high accuracy and in a very short time so as to be suitable for the racing environment.
A further general object is to provide a stud girdle which uses primarily friction forces in a ball socket joint for transmitting and equalizing vibrations and forces among the rocker valve rocker arm studs.
A further general object to provide a valve stud girdle which can readily be adapted by a splitting arrangement to divide the same amongst interspersed rocker arm studs which are canted and splayed, as is Ford Motor car engines.
Further general object of this invention is to provide a valve stud girdle assembly for engine heads which results in fewer stud failures during operation at high rpms than conventional designs.
A further object of the invention is to provide a valve stud girdle which is user-friendly by being easy to install and readily permitting valve adjustments to be made directly through the girdle while the same is fully secured in place.
These and other objects and features of the invention will be apparent from the following description and claims when taken in conjunction with the accompanying drawings, of which: